Telephone-exchange system



R. S. WILBUB.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAYI3. 191B- 1,380,451 Patented June 7, 1921.

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' RAY s. WILIBUR, or LYNDHURST, NEW JERSEY, ASSIGNOR T0 wssrnmv ELECTRIC COMPANY, INCORPORATED, on NEW YORK, in Y., A CORPORATION or NEW YO a full, clear, concise, and exact description.

. ,Thisinvention relat'esto telephone eX- change systems and more particularly to those in which interoflice trunk circuits are employed for completing connections between the oflicesa i In such systems it is desirable to provide means to enable the operator at one of the offices to readily secure the attention of the operator at the other oflice when desired.

.It is the object of this invention to provide improved signaling means for systems of this character. v

To attain this object in accordance with a feature of the invention, a trunk circuit is provided with means, operating upon the disconnection therefrom at one office, to producea momentary change of the electrical conditions of the trunk circuit existing at the other office, thereby causing the display of a supervisory signal for recalling the attention of the operator thereat,v

The nature of this invention will more fully appear from the following specification and the annexeddrawing in which the figure shows, diagrammatically jsuflicient portions of a trunk circuit. and the associated link or. connecting circuits to properlyillustrate. the invention.

In the accompanying drawing, a trunk circuit D terminates in a jack 1 at the oflice or switchboard A andin a jack 24 at the .ofiice or. switchboard B. A link circuit C which may be of any suitable type terminatin ina )lu 12, is rovided at switchboard a l s l A for connection with jack 1, while a link circuit E terminating in a plug 25 is furnished at switchboard B for connection with jack 24:. For the sake of clearness, certain portions of the linkcircuits O and E have been omitted since such portions are unessentlal to the proper understanding of the invention. A calling signal lamp 3 is associated with the trunk circuit D at switchboard A, and supervisory signal lamps 4 and .5 are associated with the link circuits C and E, respectively. 7. Itis thought that the invention may be 6, the winding of relay TELEPHONE-EXCHAN SYSTEM.

Specification of Letters Patent. Patentd.J Q7" 192 Application filed May is, 191s, Serial No. 234,347. i

ing description of the operation of the sys- A term.

Assuming that the operator at switchboard B desires to call the operator at sw1tchboard A, the insertion of plug 25 in ack 24 causes the operation of relay 6 over a clrcuit established from battery through the normal contact of relay 7 'the winding of relay 6, the right hand winding of retardatlon e011 8, the ring contacts of jack 24 and plug 25, the windings of retardation coils 9 and 10, the tip contacts of plug 25 and ack 24, and the left-hand winding of retardat1on coil 8 to ground. By. the closure of 1ts contact, relay 6 establishes a circuit extending from batter through the righthand winding of line relay 2, the righthand contact of cutoff relay 14, the ring conductor of the trunk, the contact of relay 11, the tip conductor of the trunk, the left-hand contact of relay 14, and the left-hand winding of. relay 2 to ground. Relay 2 operates to cause the lightlng of the calling signal lamp 3 over a clrcuit from battery through the lamp 3 and the contact of relay 2. to ground. Relay 11 also operates, closing its contact 18 prior to the closure of contact 17. .Upon the closure of contact 18,, a circuit is completed from battery, through contact 18 of relay 11 and the winding of relay 19 to ground. The consequent operation of relay 19 pauses thev operation of relay 7, over-a circuit extendving from battery through the contact of relay 19 and the winding of relay '7 to ground. Theopening of the normal contact of relay .7 V interrupts the connection formerly existing from the source of current to the circuit previously traced and including the winding of relay 6. The subsequent closure ofcontact 17 of relay 11 reconnects the source of currentto the circuit of relay 6' through contact 17 of relay 11, and the alternatecontact of relay 7 Supervisory lamp 5 is lighted over a circuit established from battery, through the sleeve contacts of jack 24. and plug 25, the lamp 5, andthe normal contact of relay 23 to ground.

Listening key 20 may now be actuated for the purpose of connecting the usual operators telephone circuit (notshown) at switchboard B with the link circuit E. Relay 23 is also operated thereby overa circuit established from battery through the key right-hand winding of relay 23, resistance 22 and the contact 21 of key 20 to ground,

the contact 17 of relay 11, the alternate contactof relay 7 the winding of relay 6, the

he ring contacts of jack 2% and plug 25, the retardation coil 9 and the lefthand winding and the alternate contact of relay 23 to ground. 7

In answering the call, the plug 12 is inserted in the jack 1, thereby completing a circuit from battery, through supervisory lamp 4:, resistance 13, sleeve contacts of plug 12'and jack 1, and the winding of cutoff relay 14, to ground. Relay 1 1 operates, disconnecting the line relay '2 from the trunk conductors and thereby extinguishing the calling 1amp3. Relay 15 now operates and relay 11 is maintained in an operated condition over a circuit established from battery through the winding of relay 15, the

ringicontacts of plug 12 and jack 1, the

contact of relay 6, the winding of relay 11, the tip contacts vof jack 1 and plug 12 to ground. Supervisory'lamp a is therefore prevented from lighting, due to the shunt path established .therearound through the contact of relay 15 and the resistance 16.

By the actuation of the usual listening key 26, the operator at switchboard A may converse with the operator at switchboard B over the trunk circuit E, in the usual manner.

Should the operator at switchboard B release the listening key 20, such operator may still be recalled by the operator at switchboard A, prior to the disestablishment' of the connection, by the temporary removal of plug 12 from jack 1 since the operation of relay 23 is controlled solely by the operator at switchboard A after the release of 20. Upon the removal of the plug all of the apparatus'associated with the link circuit C1 and with the trunk circuit 1) at switchboard A, will return to the normal conditions and relay 11 will release during the releasing period of the cutoff relay 1 1 and prior to the reconnection of the line relay to the trunk conductors. In releasing, contact 17 is adapted to open prior to the opening of contact 18. The source of current is, therefore, disconnected from the circuit previously traced, including the winding of relay 6 by the opening'of contact 17.

Since this circuit also includes the left-hand winding of relay 23, and since the listening key20has been released, relay 23 is looked over this circuit and upon the removal of the source of current therefrom, it is released, causing the lighting of lamp 5 over a circuit from battery, through the, sleeve contacts of jack 24: and plug 25, lamp 5 and the normal contact of relay 23 to ground.

right-hand winding of retardation coil 8,;

by the operator The control of the supervisory lamp 5 is thereby transferred 'to the operator at switchboard B. The subsequent-opening of the contact 18 of the relay 11 releases relays 19 and 7; The release of relay 7 reconnects the source of current to the circuit including relay 6 as originally traced, to again operaterelay Gand thereby repeat the series of operations accompanying the initiation of a call from switchboard B. Upon the subsequent reinsertion of the plug 12 in the jack 1, operations such as have been described in connection with the answering low. The actuation of the listening key 20 in answering the recall operates and. locks relay 23', thereby; extinguishing the lamp 5, as prevlously described and therefore preparing the link circuit E for receiving another recall upon the subsequent release of the listening key 201 It will be noted that further removals of the plug 12, from the jack 1, prior to the actuation of the listening key'20 have no efiect upon the recall signal which is continuously displayed upon the first removal of the plug.

Upon the disconnection of the link circuits C and E from the trunk circuit B, all apparatus returns to the normal position shown therefor. l r 7 It will be evident from the above description' that the attention of the operator at the switchboard B may be readily recalled by the continuous display of a supervisory signal thereat, upon the removal of the plug 12 from the jack 1, by the operator atthe switchboard A, while the subsequent reinsertion of the plug 12 in the jackl1,restores the apparatus to the-call answering condition.

What is claimed is: I V

1. In a telephone exchange system, a first and a second switchboard, a trunk circuit comprising two inductively coupled sections interconnecting the switchboards, a link .circuitat each of the switohboards for connection with the trunk circuit, a signaling circuit associated with the second switchboard, and means operated by the disconnection of a link circuit from the trunk circuit at the'first switchboard to tempoat switchboard A will fol- 3. In a telephone exchange system, a

trunk circuit interconnecting a first and a second switchboard, a link circuit at each switchboard for connection therewith, a relay having a locking winding, a supervisory signal for the link circuit at the first switchboard, and means operative upon the disconnection of the link circuit at the second switchboard to momentarily open the locking circuit of the relay thereby operating the supervisory signal.

4. In a telephone exchange system, a trunk circuit interconnecting a first and a second switchboard, a link circuit at each switchboard for connection with the trunk circuit, a calling signal at the first switchboard, a recall signal at the second switchboard, and means operative upon the disconnection of a link circuit at the first switchboard to continuously operate the recall sig nal at the second switchboard and thereafter to operate the calling signal at the first switchboard.

5. In a telephone exchange system, a trunk circuit interconnecting a first and a second switchboard, a link circuit at the first switchboard, a calling signal associated therewith at the first switchboard adapted to be efiaced upon the connection of the link circuit with the trunk circuit, a recall signal at the second switchboard, and means operative upon the disconnection of the link circuit from the trunk circuit at the first switchboard to operate the call and recall signals, said calling signal being eiiaced upon a subsequent reconnection of the link circuit with the trunk circuit, said recall signal being unaffected thereby.

6.111 a telephone exchange system, a trunk circuit interconnecting a first and a second switchboard and having its terminals connected inductively, a relay bridged across the trunk circuit at the second switchboard upon the initiation of a call from the first switchboard, a 'source of current normally connected with the trunk circuit at the first switchboard, a first circuit controlled by the relay adapted to disconnect the source of current from the trunk circuit immediately upon the release of the relay, thereby operating the signal at the first switchboard, and a second circuit controlled by the relay adapted to subsequently reconnect the source of current to the trunk circuit.

7. In a telephone exchange system, a trunk circuit, a relay at one end of the trunk circuit adapted to successively open its contacts upon its release, a signal at the other end of the trunk circuit, and means controlled by the successive opening of the contacts of the relay to cause the continuous operation of the signal. I

In witness whereof I hereunto subscribe my name this 9th day of May, A. D. 1918.

RAY S. /VILBUR. 

